Anti ice on the 747

[grind king]

Can some one tell me which surfaces use bleed air for anti-ice on the 747-400? I'm assuming the wings and horizontal stab, but am not sure of the vertical stab and engine inlets.

[323ti]

bleedair anti ice

747 deices with bleedair: wing leadingedge and engine nosecowls, tailplane doesn´t have deice.

brgds Joe

[7gcbc]

I was really surprised to find out that the bleed air holes on the wing leading edges, do not work (effectively) if you have any stage of flap selected, thus limiting holding in icing conditions to 250kts +

[Flight Detent]

7gcbc,

You're quite right, as far as you go, but that refers to the position of the leading edge k/flaps which makes the de-ice (anti-ice), system ineffective when they are extended.

And, of course, the leading edge flaps and slats are selected out by differing selections of the trailing edge flaps.

Hope that makes sense!

Cheers

[NSEU]

I was really surprised to find out that the bleed air holes on the wing leading edges, do not work (effectively) if you have any stage of flap selected, thus limiting holding in icing conditions to 250kts +

Is this written in your manuals or is this something you heard, 7gcbc?

As far as I know, the holes (slots) are simply exit points for hot bleed air circulating in the leading edge of the wing (which is the part of the aircraft being de-iced by the 747 wing anti-ice system). I don't believe the leading edge slats/flaps are being deiced at any time. The size and coverage of the exit slots is simply not great enough.



What you may be doing by extending the leading edge flaps is blocking most of the airflow to the leading edge and risking overheat of the leading edge.

Regards.
NSEU

[7gcbc]

Flight Detenent, indeed correct, I meant the leading edge ones

NSEU,

Nope, just came up in a conversation with a United 47 Capt last week (inbetween killing off major brain cells at a pub), we spoke about general handling, "Gotcha's" on the 47-400 and typical approach/config/weight.

As the modern wing is a significantly "intelligent" piece of engineering, the K's deploy forward, as the trailing edges are lowered, he basically said that in practical application of de-ice, it was not possible to hold in icing conditions with any degree of flap lowered, as the bleed air was blown up through the leading edge gaps, thus a clean 47 is practically limited to 250+ holding, this came from complying with ATC..

Crosswind landing techniques and yaw stability with 1 donkey gone and idle sink rates/max landing weight/float!! were the other areas of discussion.

I was further surprised to find that she (47 that is) is difficult to land light and she has a tendency to yaw quite vigorously with any of the outboards failing... <general handling discussion>


cheers

7gcbc (not a line pilot, just love the stuff)

[Intruder]

it was not possible to hold in icing conditions with any degree of flap lowered, as the bleed air was blown up through the leading edge gaps, thus a clean 47 is practically limited to 250+ holding

Not really true. At relatively light weights a 220-230 KIAS hold is practical.

Below 310T (metric tonnes GW), Vref+80 is flaps up maneuvering speed. Max landing weight is 302T. At 300T, Vref is 157, so min flaps up speed is 237. Note that this speed is a bit above the yellow arc, so a factor is already built in for angle of bank.

At 240T Vref is 140, making a 220 KIAS hold feasible; 230 KIAS is feasible at about 270T.

[7gcbc]

Thanks for info intruder

I now understand Weight management is a crucial part.


cheers

7gcbc

[Atlanta-Driver]

Ice

How many times has one actually use wing anti-ice on a large jet... Me only once and I come from an area where ice is a fact of life.

AD

[Intruder]

Twice in 6+ years. That includes many winter trips to ANC, SEL/ICN, and Europe.